The present invention relates to a novel arteminolide compound obtained from the flower of Artemisia sylvatica MAXIMOWICZ and designated 8-acetylarteminolide which is effective in inhibiting farnesyl-protein transferase(xe2x80x9cFPTasexe2x80x9d), a progression of the cell cycle and angiogenesis; to a process for the preparation thereof; and to a pharmaceutical composition containing same.
It has been found that ras oncogene, a well-known oncogenic gene, is activated in about 30% of human cancer cells. In order to transform cells, the Ras protein must bind to the plasma membrane, and for this binding to occur, a farnesyl group must be attached to the C-terminus thereof. Thus, it has been expected that inhibition of the FPTase involved in such farnesylation step could repress the expression of ras oncogene.
The Ras protein produced by the expression of ras oncogene has a molecular weight of 21 kDa and consists of 188-189 amino acid residues. It is capable of binding with guanine nucleotides (GDP and GTP) to act as a signal transmitting agent to growth factors. The ras oncogene, which is the first oncogenic gene found in human carcinomas, is classified into harvey-ras (H-ras), kirsten-ras (K-ras) and N-ras. More than 30% of the human cancer cells examined were found to contain mutated ras genes which produce Ras proteins (H-Ras, K-Ras and N-Ras) of abnormal biological activities. In particular, mutated ras genes have been found in 90% of exocrine pancreatic carcinoma, 50% of colon carcinoma and 50% of lung cancer cases (M. Barbacid, Ann. Rev. Biochem., 56, 779(1987)).
Normal Ras proteins are involved in the regulation of growth and division in animal cells, and like other G-proteins, must bind with GTP to become activated or xe2x80x9cswitched onxe2x80x9d as a signal transmitting agent, while it becomes deactivated or xe2x80x9cswitched offxe2x80x9d when the bound GTP thereto gets hydrolyzed to GDP (G. Bollag, Ann. Rev. Cell Biol., 7, 601(1991)).
Biochemical and structural studies have suggested that after binding with GTP, the Ras protein must be localized in the plasma membrane in order to perform its intended biological function. For the Ras protein to become functional by attaching itself to the plasma membrane, the inactive precursor produced in the cytoplasm protein must bind with lipids, more specifically, with isoprenoid derivatives generated in the steroid biosynthesis, through a series of reactions called post-translational modifications. Such lipid binding reaction, i.e., farnesylation, occurs at the cysteine residue site of the C-terminus of Ras protein containing a sequence motif expressed by CAAX, wherein C is cysteine, A is an aliphatic amino acid and X is Ser, Ala, Met or Glu, which serves as the recognition site for farnesyl-protein transferase (FPTase).
The above mentioned binding of a farnesyl group to the cysteine residue of the Ras C-terminus represents the first step of the post-translational modifications, which is followed by proteolytic cleavage of the three amino acid residues, AAX; and, finally, the cysteine residue exposed at the C-terminus is methylated. The Ras protein thus modified has a lipophilic C-terminus which interacts strongly with the plasma membrane.
The post-translational modifications described above involve three enzymes which control the farnesyl group transfer, the peptide hydrolysis and the methylation steps, respectively. An agent which suppresses the post-translational modifications by inhibiting one of the three enzymes is expected to be an effective anticancer drug. Along this line, therefore, there have been extensive studies to develop inhibitors of the enzymes for the post-translational modifications, particularly those of FPTase.
It has been observed that the FPTase isolated from mice is inhibited by compounds having the structural feature of the C-terminus of a Ras protein. Based on this observation, a number of peptide derivatives having a terminus sequence of CAAX have been synthesized and screened for their inhibitory activities (Y. Reiss, Cell, 62, 81(1990)). As a result, effective farnesyl-protein inhibitors designated as L-731,734 and L-731,735 have been developed by Merck Co.(N. E. Kohl et al., Science, 260, 1937(1993)). Meanwhile, a benzodiazepin derivative having good inhibitory activity has been discovered by Genentech Inc.(G. L. James et al., Science, 260, 1937(1993)). Also, Merck Co. has announced a developmental inhibitor designated L-744,822 which exhibits strong anti-tumor activity against carcinoma induced by transplanting ras oncogenes into nude mice (N. E. Kohl et al., Nature Med., 1, 792(1995)).
There have also been many screening studies to identify natural products which may exhibit inhibitory activity against farnesyl-protein transferase. Among those reported to have such activity are: limonene, perillic acid and dihydroperillic acid of plant-origin; 10xe2x80x2-desmethoxystretonigrin isolated from actinomycetes; chaetomellic acid A and B isolated from the culture of Chaetomella acutiseta; and zaragozic acid A and B which were earlier recognized to be squalene synthase inhibitors. Other compounds reported to be FPTase inhibitors are pepticinnamins and diepoxybenz[a]anthracene (V. Manne et al., Drug Devel. Res., 34, 121(1995); S. Omura et al., Drug Future, 19, 751(1994)).
Further, substances inhibiting the binding of Ras protein with plasma membrane exhibit activity in inhibiting the G2 to M phase progression in the cell cycle, due to its activity in inhibiting signal transmission in the cell (M. M. Feldkamo et al., Oncogene, 18, 7514(1999)). There have been other studies to develop controllers of the cell cycle with an aim to inhibit and treat cancers caused by abnormality of the cell cycle.
Angiogenesis, on the other hand, is a process of forming new blood vessels extending from existing veins and it occurs during the development and metastasis of cancer cells. As reported, this process may be facilitated by a factor called angiogenin isolated from the secretion of HT-29 human colon carcinoma cells (Vallee et al., Biochemistry, 24, 5480(1985)), while angiostatin, one of anti-angiogenic factors which suppress angiogenesis, inhibits the growth and metastasis of lung cancer cells (M. S. O""Relly et al., Cell, 79, 715(1994)). Examples of other anti-angiogenic factors are: alpha interferon which protects new born babies from lung angioma; antibodies of vascular endothelial growth factor; an anti-prostate cancer agent named genistein which is a natural product isolated from soy bean; platelet factor-4 and its peptide derivative; fumagillin and its derivative; ursolic acid; Herbimycin A; cartilage-derived inhibitor; and a synthetic compound named ovalicine.
As described above, there have been reported various FPTase, cell cycle and angiogenesis inhibitors. However there have continued to exist needs for new compounds having improved activity in said biological function. It is particularly desirable to develop an agent which is effective in inhibiting farnesyl-protein transferase, a progression of the cell cycle and angiogenesis. Such an agent would be especially useful for the prevention and treatment of various cancers and also for the treatment of angiogenesis-related diseases, e.g., rheumatism, diabetic retinopathy, chronic inflammation, retinitis and angioma.
Accordingly, it is an object of the present invention to provide a novel arteminolide derivative which can be effectively used in inhibiting farnesyl-protein transferase(FPTase), a progression of the cell cycle and angiogenesis.
It is another object of the present invention to provide a process for the preparation of said arteminolide derivative.
It is a further object of the present invention to provide a pharmaceutical composition containing an effective amount of said arteminolide derivative.
It is a still further object of the present invention to provide a method for inhibiting farnesyl-protein transferase(FPTase), a progression of the cell cycle and angiogenesis in a mammal.
In accordance with one aspect of the present invention, there is provided 8-acetylarteminolide of formula (I): 